Gollum started of as a little hobbit, until one day when he obtained the ring of power, Gollum loved the ring so much he would gloat over it day and night.

Then, the ring was taken from Gollum, and he did everything to try and get it back. Many years later Gollum finally tracked down Frodo of the Shire, all the way to Mount Doom. where he attacked Frodo and jumped of the ledge into Mount Doom after the ring.